Bis-(3,5-dimethyl-4-hydroxyphenyl)sulfone (hereinafter referred to as TMBS) and 2,2-bis-(4-hydroxyphenyl)propane (also known in the art as Bisphenol-A) have been described for use in making polycarbonate resins. U.S. Pat. No. 3,737,409, patented on June 5, 1973, describes a copolymer of the reaction product of TMBS, Bisphenol-A and a carbonate precursor wherein the bisphenol reaction mixtures of TMBS and Bisphenol-A are comprised of 40-99 weight percent of TMBS and a corresponding 60-1 weight percent of Bisphenol-A. The claims of the patent are directed to a copolymer as above described except that amount of TMBS used in the copolymer is 50-99 weight percent (and 50-1 weight percent of Bisphenol-A based on the total weight of TMBS and Bisphenol-A). Such proportions of these monomers in the manufacture of the polymer is urged by the patentee to enhance the hydrolytic stability of the resultant polycarbonate.
European Patent Publication No. 0,000,547 published July 2, 1979, discloses that copolycarbonates of an aromatic diphenol (e.g. Bisphenol-A) and an aromatic sulfonyl diphenol (e.g. bis-(alkylsubstituted-4-hydroxyphenyl)sulfone) exhibit improved heat deflection temperatures when the amount of sulfonyl diphenol is from 1% to 50% by weight of total diphenol and said sulfonyl diphenol is at least 99% pure 4-4' isomer by weight of total sulfonyl diphenol.
There is described by Serininl in Angewandte Makrom. Chemie, 55 (1976) pages 175-189 (Number 855) the manufacture of high molecular weight polycarbonates by interfacial polycondensatin of o,o,o', o'-tetramethylsubstituted bisphenols and phosgene. According to the reference, the synthesis of these polycarbonates requires the use of high concentrations of catalyst, high pH values, an excess amount of phosgene and a long condensation period. The polycarbonates are characterized by high second order transition temperatures, excellent hydrolytic stability, lower refractive indices and good thermoplastic processability. At page 182, the authors state that the polycarbonate based on bis-(3,5-dimethyl-4-hydroxyphenyl)sulfone is not melt stable.
Blends of the polycarbonate of Bisphenol A and acrylonitrile-butadiene-styrene,i.e., ABS, have been commercially employed for a long time. While the blends exhibit good mechanical compatibility, they have very poor weld-line strength and limited upper temperature stiffness. The poor weld-line strength is due to the immiscibility of Bisphenol A polycarbonate with the styrene/acrylonitrile matrix of ABS. If a modification of Bisphenol A polycarbonate could be made such that miscibility (single phase behavior) were achieved with styrene/acrylonitrile copolymer, the weld-line problem would be alleviated.
Because, the glass transition temperature of Bisphenol A polycarbonate is 150.degree. C., the use temperature of a Bisphenol A polycarbonate/ABS blend is relatively low. Only by increasing the glass transition temperature of the polycarbonate could one achieve a blend having a desirably high use temperature.
If both of these deficiencies of Bisphenol A polycarbonates could be achieved by the same modification, interesting, useful blends of the modified Bisphenol A polycarbonate with ABS would be achieved.